What temp for successful forge welds?

[windancer]

At what temp can forge welds be done?

Dave

 

 

[Dave Budd]

depends on the steel, type of weld, environment, etc.I mostly weld tool steel will stick at a bright orange but mild needs to be a bit hotter. At least thats my experience

[basher]

Solid state fusion is a process where time , temperature and pressure are all factors ( as is absence of oxides).

In industry some roll welding applications are done a low as 350C  however the pressures are huge (10's of thousands of tonnes).

 there is also the surface plate phenomenon of welding at room temperature over a long time.

 In practical smithing terms you are looking to weld the material at a temperature where it still has integrity (ie before you burn it or turn it to cheese) so carbon steels are welded at a lower temp than mild or wrought iron, which have higher melting points and can be worked hotter.

I have heard tales of smiths welding in the red range and must admit that I am sceptical of this whilst not denying that it is certainly a possibility.

My take on it is that I like to weld at a temp that is as high as possible without damaging the materials, so carbon steel is welded lower than wrought etc.

[Nobody Special]

Done asked it, everybody's gonna respond with a color, not a temp. (because how many of us have a thermometer in the forge, especially us hobby level guys?)

 

That said, to help with all the responses by color, steel incandescence starts at just visible red at about 1100, cherry at 13-1400, orange at 16-1700, yellow around 1900, and true white hot at about 2200. S'how i used to rough gauge temperature when I did casting and was to cheap to buy a high temperature thermometer.

 

Why temp? Trying to be more accurate in changing light conditions? Colorblind? Or just curious?

 

Now I'll stand back and let people kabitz about how different amounts of light makes different colors, how it's subject to interpretation, and how it's affected by the amount of carbon, vanadium, carbon nanotubules, and what the phase of the moon is when Jupiter aligns with Mars.

[basher]

if you are looking for indicators I use 2 .as colours are a really random way of transferring information (especially when jupiter aligns with Mars, that red peripheral glow really throws you off!!).

I weld with borax as a flux and I am looking for it to be bubbling around crazily (allegedly like kids running around in a play ground) I am also looking for it to smoke when pulled from the fire.

 If your borax dries up the fire is too oxidising.

 sparksas an indication  are too hot for almost all the materials I use.

 I have had a typr R thermometer in my welding forge and it read between 1350C and 1400C.

[ThomasPowers]

2300 degF is the temp often referred too but as mentioned "Solid Phase Welding"  (cf the book by Tylecote),  can occur at almost any temp below melting with enough pressure or cleanliness---see vacuum welding.

 

Galling of bolt threads is a solid phase welding process done at room temp!

 

In general higher carbon steel will weld (and burn!) at lower temps than lower carbon steels so where old zilch carbon wrought iron will do well at a snow ball heat, a high carbon billet will be destroyed at that same heat.

[Robert Yates]

depends on the steel, type of weld, environment, etc.I mostly weld tool steel will stick at a bright orange but mild needs to be a bit hotter. At least thats my experience

 

Aman this is the most reasonable answer and if you ask a 100 smiths you will get 99 answers and they may be all different .

 

Sam

[Steve Sells]

this is covered in the knife chat series, see ref, section.

[ThomasPowers]

Some of this is practiced skill as well.  I have seen Billy Merritt weld at temps I would consider on the low side for forging

[windancer]

I am welding just mild steel.

 

I am trying some welds and not certain if the steel gets hot enough in my forge to weld it.

 

The forge temp is what I am after.

 

Seen many demos, made my own Damascus [in a buddy's forge], read about everything there is on forge welding.

 

Done asked it, everybody's gonna respond with a color, not a temp. (because how many of us have a thermometer in the forge, especially us hobby level guys?)

 

So I will shoot for between 2200 and 2300 forge temp.

Thanks!

Dave

 

 

[ThomasPowers]

Forge welding is one of those things where having a pro work you through it a couple of times really makes a difference.

 

I'm guessing a propane forge since almost all solid fuel forges can get up to welding temps but many propane forges do not; others take a long time to come up to heat so you have to do other stuff for the first hour and then do your welding.

 

How much and what type of insulation does your forge have?  How big an opening?  Etc.

[SoCal Dave]

My question has always been:  If you need the metal to get to a white heat with a solid fuel forge to forge weld, why doesn't it need to be a white heat with a gas forge?

Why do most people have trouble with forge welding in a gas forge.  It is my belief that the gas forges are not getting hot enough.  They seem to be very hot, but they need that one more step up to the 2300/2400+ heat level.  Does any one know what the temperature is in a solid fuel forge when the metal gets to the white heat needed to forge weld?   

[ThomasPowers]

You don't need it that hot in a solid fuel forge and I have MELTED  steel in my propane forge before.  Accidentally when I had just relined it but had the regulator set for use with the old messed up liner.  Got busy and when I turned around to grab the piece it was a puddle!

[Rich Hale]

This is another thread that shows that we really need to look at who is providing anwers to questions such as this. For one thing i never suggest colors for folks to look for when learning to weld. In fact i use colors in my shop, I do not know if others see or interpret colors the same way I do. Nor do I know if they can do that well in changing ambient light. Basher cited a key I look for,,the appearance of the flux. I do not think I have ever seen steel white hot. If someone else was in my shop they may say they see white and at the same time i did not.
And more about what I started this with: When someone answers questions in these threads ask yourself how do you you know if they really know.
Review other items they have put on the site,  It does not take long to figure out the keyboard smiths from those with knowledge and willingness to help.In the early days of this site that list was short,,,now not so short.
Thanks to all the folks that add so much from their experiance and abilities and also the time they take to sit and type in the interest of furthering the knowledge of smithing.

[Steve Sells]

I figured that by now someone would mention that when using a known steel, we have access to the mill charts that show forging temps and welding temps, so we have a starting place...

[SoCal Dave]

First, I want to thank "Nobody Special" for directly answering the question.  Of course, given enough time, the proper heat, and conditions, you can get metal to weld by itself.  But, the question, I believe, is when you are in your shop and you have your forge fired up, what is the temp that you need to reach to forge weld.  I understand it depends on all these variable, but assume the condition are perfect, the forge is perfect, and you are perfect, the hammer is perfect, the time in the forge is perfect, the temperature outside is ideal, the flux is perfect, the mild steel is perfect, jupiter aligns with mars, and so at what temperature could you reasonably expect to take out your piece from the forge, and the way you do it is perfect, and you waist no time in hitting it perfectly to join the two pieces together. Lets say I have a pyrometer on my forge, and it's works perfectly, and I have lot of forge welding to accomplish on different days.  What would be the temperature that I would be looking for to start my forge welding.  This is all in the name of science and accuracy and astrology. Has anyone used a mill chart that shows forging temp and welding temps for mild steel and what that temperature might be?   

 

It was already suggested to look at the mill specification chats for that information, it is not the same temps for all metal combinations. What type of mild do you have? 1005 ? 1020 ? A36 isnt always mild or consistant, but many new people like to think it is.

[pike3e]

For me in my shop, like Owen, smoking borax when pulled from the forge is the best indicator. If it is smoking heavily, I don't question it and make the weld. This is with high carbon steel to make Damascus. I have successfully welded wrought iron/ high carbon san mai using the same method.

[basher]

I am wondering what you are going to measure temp with? A standard type K thermocouple will be eaten up in a welding forge in no time at all.

 as perviously stated my welding forge gets to 1350C (2460F) to 1400C (2550F) and will successfully weld carbon steel to mild steel using borax a s a flux .

 I only have one gas forge that happily welds mild steel to mild steel again with flux) and that runs up to a temp that will melt pure iron so over 1535C (2800F) forges do not last long at this temp.

 

As an aside a coke forge will get to 2000C (3630F) and charcoal a lot hotter up to 2700C   4890F.

 

 If you are looking to dry weld (ie without flux) then you will need a very hot gas forge which is in the neutral to reducing range .

 

In general excessive oxidisation is one of the main problems in a gas forge and is the worst ememy of forge welding.

[Ric Furrer]

Dave and all.....the word "successful" was used in the title.

Some can not make a successful weld under any conditions.

 

To join two metals...as has been said and referenced in R.F. Tylecote's work "Solid Phase Welding of Metals" all you need to for the mating surfaces to be oxide free and come within 4-5 Angstrom's distance. If they get close enough then the electrons can jump to the other metal and you get an inter-metalic bond. It is not strong unless more of the surface are comes into contact...so pressure is applied till the two surfaces come into more contact.

 

If heat is applied then less pressure is needed

If pressure is applied then less heat is required

If the surfaces are "perfectly clean" then room temp and gravity is required.

 

Time is also a factor as intimate contact of two contaminated surfaces can be accomplished with some time...a few hundred to thousands of years will do. It has been found that iron hinges and lead/brass bearings have welded in some old door hinges on medieval age structures...just due to time and a a tiny pressure.

 

SO..for us...it depends upon the 

way we clean the metal (some metals gain full oxide thickness in 15 minutes from cleaning so sanding a large pile of steel and welding after lunch gains you little)

the temperatures reached

flux used (or no flux) some fluxes are more better and if you use none and oxy gets in there you will have a harder time

pressure applied....steel to steel can be done with 225 tons per square inch at room temp

 

 

so your question is a good one and appears simple, but the answer can range from below room temp to just below liquid depending upon the conditions.

 

Sorry to muddy the waters.

 

A cheat can be heating to whatever, adding borax, waiting,rubbing the billet with a sharp mild steel rod...if the rod sticks then its ready. You can do it with your eye's closed.

Learned that from the late Bill Fiorini...a master by any definition.

 

Ric

[SoCal Dave]

Thanks Ric and Basher.  

[Benny 40 dave]

I have built a small natural gas. I have not been able to weld however. I can melt copper which is right at 2000 degrees. How can I get more heat?

[ThomasPowers]

Less heat out and/or more heat in.  Not knowing any of the details makes it hard to make detailed suggestions.

[Irondragon Forge ClayWorks]

Welcome aboard Benny, have you read this yet?  READ THIS FIRST   It will help you get the best out of the forum with tips like editing your profile to show your location (many answers depend upon knowing where in the world you are located). What are you trying to weld? Maybe pictures of your forge will help.

[Forgingforfun]

Propane homebrew single venturi burner , small volume,  I  have only successfully forge welded san mai and 1/4 round with all the stars aligned several times, at a very bright yellow heat...hope to solve that problem when I go to using coke to forge with, no I dont want to modify gas forge to be more reliable to do the same. Coal to coke is in my future . Heat pressure in correct amounts, ....with lack of oxidation is the the key